Arterial spin labeled carotid MR angiography: A phantom study examining the impact of technical and hemodynamic factors.

PURPOSE: To quantify the accuracy of three-dimensional (3D) radial arterial spin labeled (ASL) magnetic resonance angiography (MRA) using vascular models of carotid stenosis. METHODS: Eight vascular models were imaged at 1.5 Tesla using pulsatile flow waveforms at rates found in the internal carotid arteries (100-400 mL/min). The impacts of the 3D ASL imaging readout (fast low angle shot (FLASH) versus balanced steady-state free precession (bSSFP)), ultrashort echo time imaging using a pointwise encoding time reduction with radial acquisition (PETRA), and model stenosis severity on the accuracy of vascular model display at the location of stenosis were quantified. Accuracy was computed vis-à-vis a reference bSSFP volume acquired under no flow. Comparisons were made with standard-of-care contrast-enhanced MRA (CEMRA) and Cartesian time-of-flight (TOF) MRA protocols. RESULTS: For 50% and 70% stenoses, CEMRA was most accurate (respective accuracies of 81.7% and 78.6%), followed by ASL FLASH (75.7% and 71.8%), ASL PETRA (69.6% and 70.6%), 3D TOF (66.6% and 57.1%), ASL bSSFP (68.7% and 51.2%), and 2D TOF (65.1% and 50.6%). CONCLUSION: Flow phantom imaging studies show that ASL MRA can improve the display of hemodynamically significant carotid arterial stenosis compared with TOF MRA, with FLASH and ultrashort echo time readouts being most accurate.

Projection MR imaging of peripheral arterial calcifications.

PURPOSE: Both CT and MR angiography are accurate for the evaluation of luminal abnormalities in peripheral arterial disease (PAD). However, only CT (requiring exposure to potentially hazardous ionizing radiation) provides a reliable means to detect vascular calcifications. In this study, we demonstrate the feasibility of detecting peripheral arterial calcifications with MRI. METHODS: The institutional investigational review board approved the study. Seven patients with PAD and iliofemoral arterial calcifications shown by prior CT angiography (CTA) were studied. The imaging techniques included: 1) dual-echo three-dimensional (3D) gradient recalled echo (GRE) pulse sequence using flow compensation and in-phase echo times (TE); and 2) prototype version of 3D point-wise encoding time reduction with radial acquisition (PETRA), which enables imaging with an ultra-short TE. RESULTS: With both techniques after grayscale inversion, vascular calcifications appeared bright, as did cortical bone, and were readily distinguished from the vessel lumen and surrounding soft tissues. The location and conformation of the calcifications corresponded with CT. The second echo GRE provided the highest contrast-to-noise ratios; whereas PETRA was best suited for the creation of thick projection images. CONCLUSION: In this pilot study, MRI was able to detect vascular calcifications. Projection imaging using PETRA provided a similar appearance to, and allowed direct comparison with, CT.

Nonenhanced arterial spin labeled carotid MR angiography using three-dimensional radial balanced steady-state free precession imaging.

PURPOSE: To optimize and preliminarily evaluate a three-dimensional (3D) radial balanced steady-state free precession (bSSFP) arterial spin labeled (ASL) sequence for nonenhanced MR angiography (MRA) of the extracranial carotid arteries. MATERIALS AND METHODS: The carotid arteries of 13 healthy subjects and 2 patients were imaged on a 1.5 Tesla MRI system using an undersampled 3D radial bSSFP sequence providing a scan time of ∼4 min and 1 mm(3) isotropic resolution. A hybridized scheme that combined pseudocontinuous and pulsed ASL was used to maximize arterial coverage. The impact of a post label delay period, the sequence repetition time, and radiofrequency (RF) energy configuration of pseudocontinuous labeling on the display of the carotid arteries was assessed with contrast-to-noise ratio (CNR) measurements. Faster, higher undersampled 2 and 1 min scans were tested. RESULTS: Using hybridized ASL MRA and a 3D radial bSSFP trajectory, arterial CNR was maximized with a post label delay of 0.2 s, repetition times ≥ 2.5 s (P < 0.05), and by eliminating RF energy during the pseudocontinuous control phase (P < 0.001). With higher levels of undersampling, the carotid arteries were displayed in ≤ 2 min. CONCLUSION: Nonenhanced MRA using hybridized ASL with a 3D radial bSSFP trajectory can display long lengths of the carotid arteries with 1 mm(3) isotropic resolution.

Ungated radial quiescent-inflow single-shot (UnQISS) magnetic resonance angiography using optimized azimuthal equidistant projections.

PURPOSE: We hypothesized that non-contrast-enhanced MR angiography (NEMRA) could be performed without cardiac gating by using a variant of the quiescent-inflow single-shot (QISS) technique. METHODS: Ungated QISS (UnQISS) MRA was evaluated in eight patients with peripheral arterial disease at 1.5T. The radial acquisition used optimized azimuthal equidistant projections, a long quiescent inflow time (1200 ms) to ensure replenishment of saturated in-plane spins irrespective of the cardiac phase, and a lengthy readout (1200 ms) so that a complete cardiac cycle was sampled for each slice. Venous and background tissue suppression was obtained using frequency-offset-corrected inversion radiofrequency pulses. RESULTS: Scan time for UnQISS was 15.4 min for an eight-station whole-leg acquisition. The appearance of UnQISS MRA acquired using the body coil was comparable to electrocardiographic-gated QISS MRA using phased array coils. A small radial view angle increment minimized eddy current-related artifacts, whereas image quality was inferior with a golden view angle radial increment or Cartesian trajectory. In patient studies, ≥50% stenoses were consistently detected. CONCLUSION: Using UnQISS, peripheral NEMRA can be performed without the need for cardiac gating. The use of fixed imaging parameters and body coil for signal reception further simplifies the scan procedure.

Intracranial abscess secondary to dental infection.

We report a case of Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) bacteraemia and secondary brain abscess in a patient where periodontal disease was implicated as the probable source.

Proximal femoral anatomy in total hip arthroplasty. A tri-planar computed tomographic assessment.

The relationship between the tip of the Greater Trochanter (GT) and the centre of the Femoral Head (FH) is commonly used as reference point to align the femoral component during hip arthroplasty. We performed tri-planar computed tomography analysis of the proximal femoral anatomy in a series of 150 patients (n = 150) to accurately delineate this relationship. The mean location for the centre of the FH was 8.64 mm (95% confidence interval, 9.44-7.83) distal to the tip of the GT. The centre of the FH was found to be distal to the tip of the GT in 90.6% of cases. Hence we would suggest caution in using the tip of the GT as a reference point during total hip arthroplasty as it could be associated with an inadvertent intraoperative leg lengthening.

CT of the head for acute stroke: Diagnostic performance of a tablet computer prior to intravenous thrombolysis.

INTRODUCTION: The authors propose that tablet computers could benefit patients with acute stroke in the remote care setting, where time to and accuracy of CT interpretation greatly influences patient outcome. METHODS: One hundred and fifty consecutive patients who presented to the Emergency Department of a tertiary referral neurosciences centre within a time window suitable for intravenous thrombolytic therapy were included. Images were wirelessly transmitted to a tablet computer (iPad 3rd Generation, model = A1430, Apple, Cupertino, CA) and were reviewed by radiologists with three levels of experience for signs of intracranial haemorrhage, large vessel occlusion and parenchymal infarction. Reference standard interpretation was performed by two neuroradiologists using a diagnostic monochrome display. RESULTS: Consensus neuroradiologist review on the tablet display found and correctly classified all of the 23 cases of intracranial haemorrhage including 21 cases of parenchymal haematoma, two cases of petechial haemorrhage and one patient with an acute subdural haematoma. Less experienced readers missed cases of petechial and subdural haematomas. There was excellent agreement between the tablet and diagnostic monochrome display in cases with no infarct or extensive parenchymal infarction. CONCLUSIONS: Tablet computers can be used to facilitate rapid preliminary CT interpretation in patients with acute stroke in the remote setting.

C-reactive protein and radiographic findings of lower respiratory tract infection in infants.

AIM: To evaluate the association between C-reactive protein (CRP) and radiological evidence of lower respiratory tract infection (LRTI) in infants. METHODS: All patients aged less than 4 years who presented with suspected lower respiratory tract infection, who received a peri-presentation chest radiograph and CRP blood measurement over an 18-mo period were included in the study. Age, gender, source of referral, CRP, white cell count, neutrophil count along with the patients' symptoms and radiologist's report were recorded. RESULTS: Three hundred and eleven patients met the inclusion criteria. Abnormal chest radiographs were more common in patients with elevated CRP levels (P < 0.01). Radiologic signs of LRTI were identified in 73.7% of chest radiographs when a patient had a CRP level between 50-99 mg/L. CRP levels were a better predictor of positive chest radiograph findings for those aged greater than I year compared to those 1 year or less. CONCLUSION: CRP may be used in patients with suspected LRTI diagnosis to select those who are likely to have positive findings on chest radiograph, thus reducing unnecessary chest radiographs.